Nokia 4A0-102 Exam - Topic 1 Question 78 Discussion

Actual exam question for Nokia's 4A0-102 exam

Question #: 78
Topic #: 1

A confederated AS is comprised of three members. One member is comprised of 4 routers, while the other two members are comprised of 3 routers each. Assuming member ASs are fully meshed and use full mesh iBGP, what is the required number of BGP sessions within the confederation?

A12

B13

C14

D15

Show Suggested Answer

Suggested Answer: D

by Hermila at Mar 20, 2025, 08:44 PM

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Flo

8 months ago

Definitely 15 sessions, trust me on this!

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Dorothy

9 months ago

No way, it should be 14!

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Kris

9 months ago

I think it's 12 sessions, right?

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Lorrine

9 months ago

Wait, how do we even get to that number?

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Cherri

9 months ago

There are 10 routers total in the confederation.

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Roosevelt

9 months ago

I feel like the total sessions should add up from each AS, but I can't remember if we need to account for any overlaps. I hope I got this right!

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Elvera

10 months ago

If I recall correctly, for a full mesh, the formula is n(n-1)/2 for each AS, but I’m a bit confused about how to combine them in a confederation.

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Shad

10 months ago

I think we need to consider the number of routers in each AS and then calculate the sessions for each member. It feels similar to a practice question we did on full mesh iBGP.

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Christene

10 months ago

I remember something about calculating BGP sessions based on the number of routers, but I'm not sure how to apply it here with the confederation setup.

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Carey

10 months ago

Alright, time to put pen to paper and work through this systematically. I'm feeling more confident now that I've heard a few different approaches.

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Pete

11 months ago

I think I've got it! For a full mesh iBGP, each router needs a session with every other router. So the total number of sessions should be the sum of the number of sessions for each member AS.

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Luisa

11 months ago

I'm a bit confused on how the full mesh iBGP comes into play here. Gotta make sure I understand that concept before I can solve this.

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Mabelle

11 months ago

Okay, let me break this down step-by-step. We have 3 member ASs, with 4, 3, and 3 routers respectively. That's 10 routers total.

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Eladia

11 months ago

Hmm, this looks like a tricky one. I'll need to think through the iBGP full mesh requirements carefully.

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Levi

1 year ago

Because each router in the fully meshed member ASs needs to establish a session with every router in the other member ASs, so it's 4 routers x 3 routers + 3 routers x 3 routers = 12 + 9 = 21. But since iBGP sessions are not required within the same member AS, we subtract 7 (3 routers x 2 sessions) to get 14.

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Lizbeth

1 year ago

Why do you think it's 14?

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Ryann

1 year ago

I feel like I need a diagram to visualize this. Or maybe a cup of coffee to help me focus. Either way, I'm going to give this my best shot.

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Alisha

1 year ago

D) 15

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Jin

1 year ago

C) 14

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Vicky

1 year ago

B) 13

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Vernell

1 year ago

A) 12

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Maybelle

1 year ago

D) 15

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Annmarie

1 year ago

C) 14

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Ashlee

1 year ago

B) 13

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Sheridan

1 year ago

A) 12

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Claudio

1 year ago

C) 14

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Laticia

1 year ago

B) 13

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Val

1 year ago

A) 12

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Levi

1 year ago

I disagree, I believe the answer is C) 14.

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Jose

1 year ago

Haha, this question is like a game of connect the dots, but with routers instead of, well, dots. I'm going with D, just to see if I can beat the system!

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Alberta

1 year ago

Okay, let's think this through. If each member AS is fully meshed, that means we have 4 + 3 + 3 = 10 routers, and each router needs to connect to every other router, so that's a lot of sessions.

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